US8430643B2 - Volumetric fluidics pump method with translating shaft - Google Patents

Abstract

A pump for moving a fluid through a fluidics system includes a surface and channel disposed along at least a portion of the surface. The pump also includes a driving mechanism having a rotatable shaft and a plurality of haptics operably coupled to the shaft. A closed portion is formed in the channel as the channel is compressed between the surface and at least one of the haptics, the closed portion having a thickness between the surface and the haptic. The pump additionally has a circular path and a shaft path. The surface has a radius of curvature in the vicinity of the closed portion that is greater than the sum of a radius of the circular path and the thickness of the closed portion.

Description

This application is a divisional application and claims priority to U.S. application Ser. No. 11/832,782, entitled “Volumetric Fluids Pump with Translating Shaft Path”, filed on Aug. 2, 2007, the entire contents of which are hereby incorporated by reference in their entirety for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a volumetric fluidics pump, and more specifically to pump including a shaft or rotor that moves relative to a fluidic channel.

2. Description of the Related Art

Volumetric pumps may be advantageously utilized in a broad range of applications and offer various advantages such as precise control of a volumetric flow rate and preservation of a sterile environment. For example, in ocular surgical applications such as cataract surgery, peristaltic pumps are often used to maintain a critical balance between the flow of fluid into and out of the eye.

In a typical system, the peristaltic pump comprises a tube or channel that is continually closed between a ramp and one or more rollers disposed about a rotating pump head. As the pump head rotates, a first rollers engages the tube on an inlet side and draws fluid into a tube section that is subsequently sealed off by an adjacent, second roller. Once the tube section is sealed, the first roller opens the tube, thus allowing the second roller to push entrapped fluid out of the tubing section, while simultaneously drawing in new fluid. In order for the roller to close off the tubing, the mating ramp is arcuate in shape and generally has a radius of curvature that equals the sum of the radius of the circular roller path plus the thickness of the tube as it is squeezed between the ramp and one of the rollers.

One problem with such peristaltic pump designs is that in order to prepare the pump for operation, the ramp must be displaced from the pump head, the pump tubing arranged around the rollers, and the ramp moved back into place over tube. In addition, a relatively complex and expensive latching mechanism may be required to keep the tubing engaged between the rollers and ramp. Another potential problem is the time and difficulty involved in arranging the tubing around the rollers, which usually requires two hands.

In light of these problems, improved volumetric pumping devices and methods are needed that provide less expensive pumping components and simpler installation procedures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention may be better understood from the following detailed description when read in conjunction with the accompanying drawings. Such embodiments, which are for illustrative purposes only, depict novel and non-obvious aspects of the invention. The drawings include the following figures:

FIG. 1 is a perspective view of a pumping mechanism according to an embodiment of the present invention.

FIG. 2 is a front view of the pumping mechanism illustrated inFIG. 1

FIGS. 3A-3E are front views of the pumping mechanism illustrated inFIG. 1 and show operation of pump as it draws fluid therethrough.

FIG. 4 is a front view of a pumping mechanism according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are directed to volumetric pump assemblies, procedures, and methods. Embodiments of the invention may be particularly suited for use in medical devices or surgical systems, for example, in ophthalmic surgical systems such as phacoemulsification systems used in preparing an eye for the implantation of an intraocular lens.

Volumetric pumps according to embodiments of the invention generally comprise a rotating pump head that includes a plurality of haptics, fingers, or rollers that contact a channel or tubing portion through which fluid is pumped. The pump may be configured to allow the haptics to move over or along a ramp surface that is flat or that has a radius of curvatures that is relatively large in comparison to the distance from the center of the pump head to a distal portion of the haptics used for transferring fluid through the pump. The ramp surface may be characterized by a single radius of curvature or may be a more complex shape, such as an aspheric shape and/or a shape characterized by two or more radii of curvature.

Referring toFIGS. 1 and 2, in certain embodiments of the present invention, apumping system10 comprises asurface12, achannel14 for transferring fluid, and adriving mechanism18 that is configured transfer fluid through thechannel14 during operation of thepumping system10. Thedriving mechanism18 comprises arotatable shaft20 disposed about anaxis21 and a plurality ofhaptics22 that are operably coupled to theshaft20. Thechannel14 comprises a closedportion24 that is compressed between thesurface12 and at least one of thehaptics22, the closedportion24 having a thickness t between the surface and an individual haptic22. Thehaptics22 are disposed inside acircular path28 having a radius R, the distal portion of each haptic22 traveling along thecircular path28 during operation of thepumping system10. Conveniently, thecircular path28 may be defined as a locus of points about theaxis21 of theshaft20 that arc traversed by a mostdistal point30 of a haptic22 as it revolves about theaxis21.

Thedriving mechanism18 is generally configured to cause thehaptics22 to sequentially compress and close thechannel24, and to move along thesurface12 in a way that draws fluid in from aninlet side32 and forces fluid out at aninlet side34. Thedriving mechanism18 may comprise a case orhousing38 that may include a driving motor, gear mechanism, linkage mechanism, and/or the like (not shown) that are configured to drive the shaft orrotor20 and thehaptics22. Thedriving mechanism18 may be configured so that thehousing38 moves with theshaft20 during normal operation of thepumping system10. Alternatively, as illustrated inFIGS. 1 and 2, thedriving mechanism18 may be configured so that the shaft moves relative to thehousing38 normal operation of thepumping system10. In the later case, an aperture, slot, or opening40 in thehousing38 may be provided to allow free movement of theshaft20 relative to thehousing38.

Thechannel14 may be made of a resiliently deformable and/or elastomeric tube or tubing portion through which fluid flows into and out of thepumping system10. In certain embodiments, thechannel14 comprises a molded fluid channel, for example, like that disclosed in U.S. Pat. No. 6,962,488, which is herein incorporated by reference in its entirety. Thechannel14 is generally part of a fluidic tubing system through which fluid flows. For example, thechannel14 may be part of a fluidics cassette that provides aspiration, irrigation, and other fluidic functions for an ocular surgical system, such as fluidics cassettes disclosed in co-pending U.S. patent application Ser. Nos. 11/530,306, 11/558,403, 11/558,434, 11/558,437, and 11/558,416, all of which are herein incorporated by reference in their entirety.

Thehaptics22 may be in the form of rollers that engage and squeeze thechannel14 during operation of thedriving mechanism18. Therollers22 are generally of made of a relatively hard and/or rigid material that deforms the relativelyflexible channel14. Therollers22 may be rotatably mounted to a hub to reduce or eliminate rubbing between therollers22 and the exterior surface of thechannel14.

Thesurface12 may be flat, as illustrated inFIGS. 1 and 2. Alternatively, thesurface12 may have a more complex profile along the direction of motion of thehaptics22. For example, thesurface12 may comprise an arcuate profile that is characterized by one or more radii of curvature and/or defined by a polynomial, trigonometric, or some other function. In any event,surface12 is generally relatively flat compared to a conventional peristaltic pumping system. The relatively flat profile of thesurface12 allows thechannel14 to be easily arranged within thepumping system10 during preparation and use. In some embodiments, the radius of curvature of thesurface12 in the vicinity of the closedpotion24 is greater than the sum of the radius R of thecircular path28 plus the thickness t of the closedportion24. Because of this geometric relationship, theshaft20 may be moved during operation in a direction that is generally normal to thesurface12, thus maintaining the closedportion24 as the haptics rotate about theshaft20.

In this regard, thepumping system10 further comprises ashaft path42 that is traversed byshaft20 during operation of thepumping system10 ordriving mechanism18. The resulting motion of eachhaptics22, relative to a fixed reference (e.g., relative to the surface12), is a combination of motion of each haptic22 about the shaft20 (e.g., along the circular path28) and the motion of theshaft20 along theshaft path42. The motion of each haptic22 results in a haptic path portion that is along at least a portion of thesurface12 and allows each haptic22 to keep thechannel14 closed until the succeeding haptic22 also closes thechannel14.

The operation of thepumping system10 and path of thehaptics22 along thesurface12 may be illustrated with reference toFIGS. 3A-3E. InFIG. 3A, a first haptic22acomes into contact with thechannel14 and forms a firstclosed portion24a. When the firstclosed portion24ais initially formed, theaxis21 of therotatable shaft20 is at a height h₁above thesurface12. As thedriving mechanism18 rotates about the axis21 (counter clockwise inFIGS. 3A-3E), fluid is drawn into thepumping system10 from theinlet side32 and is pushed out of theoutlet side34. In order to maintain the firstclosed portion24aduring rotation of theshaft20, a bias force F may be provided to overcome the resiliency of thechannel14. In the illustrated embodiment shown inFIGS. 3A-3E, the bias force is provided by aspring42 that is coupled on one end to thehousing38 and on the other end to a base44 that is generally fixed relative to thesurface12. Alternatively or additionally, the bias force may be produced by the mere weight of thedriving mechanism18, by a cam, and/or some other biasing device or mechanism is used to provide a predetermined biasing force F that is suitable for closing off thechannel14 between thesurface12 and the first haptic22a.

As thedriving mechanism18 continues to rotate, the height of theaxis21 above thesurface12 increases to a maximum height h₂. As illustrate inFIG. 3C, further rotation ofmechanism18 results in a decrease in height (e.g., height h₃) as the bias force F pushes theaxis21 toward thesurface12 to maintain the firstclosed portion24aof thechannel14. As illustrated inFIG. 3D, themechanism18 continues to rotate until a second haptic22bcontacts thechannel14 and forms a secondclosed portion24bthat defines aclosed volume48 of fluid. At this point, the height of theaxis21 above thesurface12 reaches a minimum height h₄. Referring toFIG. 3E, further rotation results in a new cycle in which fluid from theclosed volume48 flows past the haptic22aas thechannel14 opens between thesurface12 and the haptic22a.

Pumping systems according to embodiments of the invention may include features other than those illustrated for thepumping system10. Referring toFIGS. 4aand4b, another embodiment of the invention comprises apumping system110 includes adriving mechanism118 that comprises ahousing138 and fourhaptics122 disposed about anaxis121. Thepumping system110 also includes achannel114 disposed between thehaptics122 and asurface112 that has a convex shape. As illustrated by comparingFIG. 4A withFIG. 4B, theentire driving mechanism118 moves in a direction that is substantially perpendicular to thesurface112 as the driving mechanism rotates about theaxis121. Similar to thepumping mechanism10, thepumping mechanism110 provides aclosed portion124 of thechannel114 that is configured to draw fluid through thepumping mechanism110 as thedriving mechanism118 moves succeeding haptics along thesurface112.

The above presents a description of the best mode contemplated of carrying out the present invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains to make and use this invention. This invention is, however, susceptible to modifications and alternate constructions from that discussed above which are fully equivalent. Consequently, it is not the intention to limit this invention to the particular embodiments disclosed. On the contrary, the intention is to cover modifications and alternate constructions coming within the spirit and scope of the invention as generally expressed by the following claims, which particularly point out and distinctly claim the subject matter of the invention.

Claims (2)

What is claimed is:

1. A method of pumping a fluid, comprising:

providing a surface, a shaft, a shaft path, and a plurality of haptics operably coupled to the shaft;

disposing a channel between the surface and the haptics, wherein the channel is configured to have a closed portion when compressed between the surface and one of the haptics, the closed portion having a thickness defined by a distance between the surface and the haptic that closes the channel;

moving the haptics along a circular path about the shaft;

moving the shaft relative to the surface and the shaft path, wherein the surface has a radius of curvature in the vicinity of the channel that is greater than the sum of a radius of the circular path and the thickness of the closed portion;

while moving the haptics and the shaft, traversing at least one of the haptics along the surface so that the at least one haptic maintains the channel in a closed condition,

wherein a length from a center of the shaft to a distal end of one of the haptics is greater than the distance between the surface and the center of the shaft when the channel is in its least compressed state during rotation of the shaft;

moving the shaft along the shaft path radially away from the surface when at least one of the haptics traverses along a portion of the surface.

2. The method ofclaim 1, further comprising, traversing a first haptic of the plurality and a second haptic of the plurality along the surface so as to produce a closed fluid volume within the channel, the closed fluid volume being disposed between the first haptic and the second haptic.

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